Project Summary Although the small vessel consequences of type 2 diabetes in peripheral organs are fairly well understood, the effects of diabetes on cerebral microvasculature are largely unknown. A significant impediment to understanding these changes has been the technical challenges associated with complete three-dimensional mapping of small vessel network topology in vivo. The technical challenge lies in the ability to capture vessel morphology on the capillary scale while also spanning the entire cortical thickness and extending into the subcortical regions. Further complicating the technical challenge is the fact that vessel networks vary significantly in baseline structure and response to pathological perturbations across animals, thus vessel networks must be followed longitudinally to capture these dynamics. Therefore, the goal of this proposal is to overcome these technical limitations by developing new optical microscopy techniques that permit complete 3D mapping of the entire cortical microvascular network structure in vivo, and to use these techniques to quantify chronic alterations in cerebral microvasculature associated with type 2 diabetes in mice. We will introduce new advances to two- and three-photon fluorescence microscopy that will significantly improve our ability to image microvascular networks in vivo at depths up to 1.5 mm over large spatial extents of mouse cortex. We will develop a new spatially offset two-color multiphoton excitation approach that utilizes recent advances in long wavelength, synchronized ultrafast lasers. The large-scale images of cortical and sub-cortical vasculature will allow full 3D vectorization of vascular networks that will enable detailed analysis of the microvascular morphology over time. We will use this combination of advanced in vivo microscopy, novel ultrafast lasers, and computational analysis of vascular networks to quantify the structural changes in cerebral microvasculature associated with type 2 diabetes.